Fixation of heat sink on sfp/xfp cage

ABSTRACT

An apparatus and system for a heat sink assembly, and a procedure for forming a heat sink assembly. The heat sink assembly includes a heat sink having a base and fins extending from the base, and a spring clip disposed on the heat sink between the fins. The spring clip includes a first tab that forms a first angle with respect to the base of the heat sink and including a second tab that forms a second angle with respect to the base of the heat sink. The first and second tabs are attached to the circuit board. By virtue thereof, a heat sink attachment to cage is provided that is space-efficient and permits a higher density of cages on a circuit board than do conventional arrangements.

FIELD OF THE INVENTION

Example embodiments described herein relate generally fixation of heatsinks to circuit boards and, more specifically, fixation of a heat sinkto a SFP/XFP cage mounted on a circuit board.

DESCRIPTION OF RELATED ART

The small form-factor pluggable (SFP) is a standard for compact,hot-pluggable transceivers used for both telecommunication and datacommunications applications. The ten gigabit small form-factor pluggable(XFP) is a standard for transceivers for high-speed computer network andtelecommunication links that use optical fiber. SFP and XFP transceiversare typically inserted into circuit board-mounted receptacles, termed“cages” to retain the SFP and XFP transceivers for connection tocomponents on a circuit board. A transceiver typically generates heatwhen it is powered and retained in a cage. The SFP and XFP cages aretypically constructed of metal and are typically designed to bebezel-mounted to a circuit board, (e.g., an I/O panel) with compliantpins for pressing onto the circuit board.

Heat sinks are typically used to dissipate heat generated by atransceiver retained in a cage. For each transceiver, the heat generatedis transmitted through a corresponding cage and a heat sink in contactwith the metal cage. Typically, the heat sink is retained in contactwith the cage using a spring clip that presses the heat sink in contactwith the cage.

An example of a typical arrangement of a heat sink attached to a cage isshown in FIG. 1, which is an isometric view showing an upper part and aside of a circuit board 104. In FIG. 1, a plurality of cages 102 arespaced from each other across the front of the circuit board 104. Gaps106 between adjacent cages 102 provide space for spring clips 108 tomount to the sides of the cages 102. Specifically, along the top edges110 of the cages 102 are a plurality of holes that receive the springclips 108 that are each bent to apply a compressive force to press arespective heat sink 112 into contact with a corresponding upper surface114 of one of the cages 102.

The arrangement shown in FIG. 1 however requires that each spring clip108 and/or heat sink 112 extend into the gap 106 between adjacent cages102. In order to maximize the density of cages 102 on the board 104, thedimensions of the gap 106 would have to be made smaller. However, if thegap 106 is made too small, there will not be sufficient space availableto dispose the spring clips 108 in the gap 106.

SUMMARY

The above and other limitations are overcome by an apparatus and asystem for a heat sink assembly, and by a procedure for forming a heatsink assembly.

In accordance with one example embodiment herein, the heat sink assemblyincludes a heat sink having a base and fins extending from the base, anda spring clip disposed on the heat sink between the fins. The springclip includes a first tab that forms a first angle with respect to thebase of the heat sink and includes a second tab that forms a secondangle with respect to the base of the heat sink.

In accordance with another example embodiment herein, the systemincludes a circuit board having one or more cages mounted thereto, whereeach cage has an upper surface formed with an opening therethrough, anda heat sink assembly mountable on at least a respective one of thecages. The heat sink assembly includes a heat sink having a base andfins extending from the base, and a spring clip disposed on the heatsink between the fins. The spring clip includes a first tab that forms afirst angle with respect to the base of the heat sink and includes asecond tab that forms a second angle with respect to the base of theheat sink.

In accordance with another example embodiment herein, the procedureincludes placing the heat sink assembly on a cage of a circuit board andsecuring the first and second tabs to the circuit board.

The example embodiments described herein provide for a heat sinkattachment to cage such as a transceiver cage (e.g., an SFP/XFP cage)that is space-efficient so that extra spaces need not be provided on acircuit board between adjacent cages for attachment of a heat sink tothe cages. Accordingly, the example embodiments described herein permita higher density of cages on a circuit board than do conventionalarrangements.

Additional features and benefits of the exemplary embodiments willbecome apparent from the detailed description, figures and claims setforth below.

DESCRIPTION OF DRAWINGS

The teachings claimed and/or described herein are further described interms of exemplary embodiments. These exemplary embodiments aredescribed in detail with reference to the drawings. These embodimentsare non-limiting exemplary embodiments, wherein:

FIG. 1 shows an isometric view showing an upper part and a side of acircuit board.

FIG. 2 shows an isometric view showing an upper part and side of acircuit board arranged in accordance with an example aspect of thepresent application.

FIG. 3A shows an isometric view showing an upper part and a side of aheat sink assembly constructed in accordance with an example aspect ofthe present application.

FIG. 3B shows an exploded view of a portion of the heat sink assemblyshown in FIG. 3A.

FIG. 3C shows an exploded view of another portion of the heat sinkassembly shown in FIG. 3A.

FIG. 3D shows a section view of the heat sink assembly, taken alongsection FIG. 3D-FIG. 3D shown in FIG. 3A.

FIG. 4 is an assembly drawing showing a portion of a circuit boardconstructed in accordance with an example aspect herein, and the heatsink assembly shown in FIG. 3A.

FIG. 5 shows a section view of the circuit hoard and heat sink assembly,taken along section FIG. 5-FIG. 5 shown in FIG. 4.

FIG. 6 is an assembly drawing of another heat sink arrangement inaccordance with an example aspect herein.

DETAILED DESCRIPTION

Those of ordinary skill in the art will realize in view of thisdescription that the following detailed description of the exemplaryembodiments is illustrative only and is not intended to be in any waylimiting. Other embodiments will readily suggest themselves to suchskilled persons having the benefit of this disclosure. Reference willnow be made in detail to implementations of the exemplary embodiments asillustrated in the accompanying drawings. The same reference numberswill be used throughout the drawings and the following detaileddescription to refer to the same or like parts.

FIG. 2 shows a circuit board 200 having a plurality of SFP cages 202 andXFP cages 204 arranged along a front edge 206 of the circuit board 200.In the specific example illustrated, the circuit board 200 has ten SFPcages 202 and two XFP cages 204. Each of the cages 202, 204 is openalong the front edge 206 of the circuit board 200 in order to receive amodule 500 (FIG. 5). Each of the cages 202, 204 extends diagonally withrespect to the front edge 206 toward a rear edge 208 of the circuitboard 200. While the cages 202, 204 are shown extending diagonally, inother embodiments the cages 202, 204 can extend at other angles such asperpendicular with the front edge 206 of the circuit board 200, or atother orientations. Each of the cages 202, 204 has an upper surface 210,which is constructed to contact a heat sink 300 (FIG. 3A), to bediscussed below. The upper surface 210 has at least one opening 212. Inthe embodiment shown in FIG. 2, the cages 202, 204 include onerectangular opening 212, which is constructed to align with and receivea portion of the heat sink 300. The cages 202, 204 shown in FIG. 2 arearranged so that there is substantially no (or minimal) gap betweenadjacent cages 202, 204.

FIG. 3A shows a view of an upper side of a heat sink assembly 302 thatincludes heat sink 300 and a spring clip 304. The heat sink 300 includesa base 306 and a plurality of fins 308 extending upwardly in FIG. 3Afrom the base 306. As would be appreciated by those of skill in the artin view hereof, the fins 308 are arranged to conduct heat away from thebase 306 and dissipate heat by convection.

The spring clip 304 has a central serpentine portion 310, a first tab312 extending from the serpentine portion 310, and a second tab 314extending from the serpentine portion 310. The spring clip 304 is fixedto the heat sink 300 between some of the fins 308 by snap fitconnection. As shown in FIGS. 3B and 3C, at two locations on the heatsink 300, opposite ends of the serpentine portion 310 are respectivelysnap fit between adjacent fins 308 of the heat sink 300.

As shown in FIG. 3D, the serpentine portion 310 of the spring clip 304extends in a plane substantially parallel to the upper surface of thebase 306 of the heat sink 300. In an uncompressed state shown in FIG.3D, the first tab 312 extends at a first angle θ₁with respect to theupper surface of the base 306. The first tab 312 extends from theserpentine portion 310 to a first free end 316. Also, in an initial,uncompressed state shown in FIG. 3D, the second tab 314 extends at asecond angle θ₂with respect to the upper surface of the base 306. Thesecond tab 314 extends from the serpentine portion 310 to a second freeend 318 which is formed as a u-shaped hook (FIG. 3A).

Also, as shown in FIG. 3D, a lower side 320 of the base 306 has a raisedsection 322 surrounded by a rectangular bezel (not shown). A front edge328 and a rear edge 330 of the raised section 322 are beveled.

The heat sink 300 is generally formed from a metal, such as aluminum.The spring clip 304 is generally formed from a metal, such as steel, andis resilient so that the first and second tabs 312 and 314 can becompressed downward toward the base 306 of heat sink 300 without anypermanent deformation of the spring clip 304. The arrangement of thespring clip 304 facilitates uniformly transmitting the spring force tothe heat sink 300 so that suitable contact pressure is applied betweenthe heat sink 300 and a respective cage 202, 204 when a module 500 (FIG.5) is not inserted in the cage 202, 204 and between the heat sink 300and the module 500 when the module 500 is inserted in the cage.

Circuit board 200 is shown in FIG. 4 with a front retaining member 402that extends across the front edge 206 of circuit board 200. Above (andoffset from) each cage 202, 204 a corresponding hole 404 is formed inthe retaining member 402 of circuit board 200. Each hole 404 in theretaining member 402 is constructed to receive and retain the first freeend 316 of the first tab 312 of the spring clip 304. Rearward of eachcage 202, 204 is a corresponding anchor 406 that is soldered on thecircuit board 200. In the example embodiment shown in FIG. 4, eachanchor 406 extends upwardly from the circuit board 200 and is a u-shapedlatch to latch onto the second free end 318 of the second tab 314. Thus,in the example embodiment shown in FIG. 4, for each cage 202, 204 thereis at least one corresponding hole 404 in the front retaining member 402and at least one corresponding anchor 406 in the board 200.

The heat sink assembly 302 is assembled onto the board 200 as follows,in one example embodiment. The heat sink assembly 302 is oriented over acorresponding one of the cages 202, 204 so that the first tab 316extends toward the front edge 206 of the board 200 and the second tab314 extends toward the rear edge 208 of the board 200. The first end 316of the first tab 312 is inserted into a hole 404 in the front retainingmember 402 and the raised portion 322 of the heat sink 300 is insertedinto the rectangular opening 212 in the cage 202, 204 corresponding tothe hole 404 in which the first end 316 was inserted. The second tab 314is compressed toward anchor 406 corresponding to the cage 202/204 untilthe second free end 318 latches onto the anchor 406.

As shown in FIG. 5, the cages 202, 204 are constructed to receive amodule 500, which includes electrical and optical modules. When the heatsink assembly 302 is attached to the circuit board 200 and no module 500is present in a corresponding one of cages 202, 204, the spring clip 304of the heat sink assembly 302 is compressed an initial amount so as toforce the bezel of heat sink 300 downwardly to contact the surface 210of cage 202, 204 in a seated position. When the heat sink 300 is seated,the raised section 322 of heat sink 300 extends through a respectiveopening 212 in the corresponding cage 202, 204. Thus, when the module500 is not present in the cage, the raised section 322 extends slightlyinto cage 202, 204.

When the module 500 is first introduced into a respective cage 202, 204(as shown in FIG. 5), there will be interference between the module 500and the raised section 322 extending into the respective cage 202, 204.Owing to the beveled front edge 328 of the raised section 322, whichacts as a guide surface, when module 500 is first inserted into therespective cage 202, 204 on which heat sink 300 is seated, module 500contacts the front edge 328 and displaces the raised section 322upwardly. As raised section 322 is displaced upwardly, the spring clip304 is further compressed beyond its initial compression before module500 was inserted in the cage 202, 204. The spring force exerted by thespring clip 304 urges the raised section 322 to contact the module 500with suitable pressure to promote conductive heat transfer from themodule 500 to the heat sink 300.

The dimensions and positions of the first tab 312 and second tab 314 aresuch that the torque (Mo(Fa)) exerted on the spring clip 304 by thefirst tab 312 about point “o” is almost equal and opposite to the torque(Mo(Fb)) exerted on the spring clip 304 by the second tab 314 aboutpoint “o”, when the first end 316 is in hole 404 and the second end 318is latched to anchor 406. The substantially equal and opposite torquesMo(Fa) and Mo(Fb) permit suitable and even pressure to be appliedbetween raised portion 322 of heat sink 300 and module 500 to enableheat transfer from module 500 to heat sink 300, which is then convectedto air through fins 308.

The beveled front edge 328 and rear edge 330 shown in FIG. 3D facilitateplacement of the heat sink 300 on a respective one of the cages 202, 204and facilitate self-seating of the heat sink 300 should the heat sinkassembly 302 be displaced at least partially from opening 212, such aswhen module 500 is first inserted into a respective cage 202, 204.

Also, the raised section 322 is located closer to a front end 324 of theheat sink 300 than it is to a rear end 326 of the heat sink 300. Theoff-center raised section 322 further facilitates positioning andalignment of the heat sink assembly 302 with respect to a respective oneof cages 202, 204 by providing a visual indication that the heat sinkassembly 302 is oriented properly or improperly with the first tab 312extending toward the front edge 206 of the circuit board 200 and thesecond tab 314 extending toward the rear edge 208 of the circuit board200, as is shown in FIG. 4. As but one example of a visual indicatorthat the heat sink assembly 302 may be improperly oriented, if theraised section 322 is inserted into an opening 212, and the bezelsurrounding the raised section 322 is seated on upper surface 210 of acage 202, 204, and the heat sink assembly 302 is oriented such that thesecond tab 314 extends towards front edge 206 of circuit board 200instead of towards the rear edge 208 of circuit board, then the secondend 318 will not be positioned relative to the circuit board 200 in amanner to enable it to be attached to the circuit board 200, asdescribed in detail above.

FIG. 6 shows an alternative example embodiment of a heat sinkarrangement of a plurality of heat sink assemblies 602 assembled ontothe circuit board 200. The heat sink assemblies 602 are the same as heatsink assemblies 302, except that the heat sink 600 included with eachheat sink assembly 602 is different than the heat sink 300 included witheach heat sink assembly 302. In particular, in the embodiment shown inFIG. 6, a retention slot 604 is formed in each heat sink 600 to receivea wall 608 of a metal cover 606. At least one ventilation opening 612 isformed in the cover 606. The heat sink assemblies 602 are fixed to thecircuit board 200 in the same way as they are for the heat sinkassemblies 302 described above. When the heat sink assemblies 602 arefixed to the circuit board 200, the retention slots 604 of the heatsinks 600 align in a substantially straight line 614, which is shownbeing substantially parallel to the front edge 206 of the circuit board200. Once the heat sink assemblies 602 are fixed to the circuit board200, the wall 608 of the cover 606 is inserted into the alignedretention slot 604 and the cover 606 is secured to the retaining member402 with screw fasteners 616.

The metal cover 606 is removably attached to the retaining member 402with screw fasteners 616. As shown in FIG. 6, the cover 606 is notattached to retaining member 402, but is disposed slightly aboveretaining member 402. The cover 606 can be removed to permit the heatsink assemblies 602 to be installed and removed. When the cover 606 isattached to retaining member 402 with the wall 608 disposed in retentionslots 604, the wall 608 limits movement of each heat sink 600 in afront-to-back, longitudinal direction along the upper surface 210 of itscorresponding cage 202, 204, as well as limits movement in anup-and-down direction. Thus, displacement of the heat sink assemblies602 caused by, for example, inserting and removing a module 500 (FIG. 5)from a respective cage 202, 204, can be limited.

The example embodiments described herein provide for a heat sinkattachment to cage such as a transceiver cage (e.g., an SFP/XFP cage)that is space-efficient so that extra spaces need not be provided on acircuit board between adjacent cages for attachment of a heat sink tothe cages. Accordingly, the example embodiments described herein permita higher density of cages on a circuit board than do conventionalarrangements.

While particular example embodiments have been shown and described, itwill be obvious to those of skills in the art that based upon theteachings herein, changes and modifications may be made to the exampleembodiments without departing from these embodiments and their broaderaspects. Therefore, the appended claims are intended to encompass withintheir scope all such changes and modifications as are within the truespirit and scope of the exemplary embodiments.

1-20. (canceled)
 21. A spring clip comprising: a first tab; a secondtab; and a serpentine portion interposed between the first tab and thesecond tab, wherein the first tab forms a first angle with respect toabase of a heat sink, the second tab forms a second angle with respectto the base of the heat sink, and the serpentine portion extends in itsentirety in a plane that is substantially parallel to an upper surfaceof the base of the heat sink, and wherein the first tab and the secondtab are capable of being respectively compressible compressed in adirection toward the base of the heat sink.
 22. The spring clipaccording to claim 21, wherein the heat sink has the base, finsextending from the upper surface of the base, a raised portion extendingfrom a lower side of the base that is opposite from the upper surface.23. The spring clip according to claim 22, wherein the raised portion isoff-center along the lower side of the base.
 24. The spring clipaccording to claim 23, wherein the raised portion has a beveled frontedge and a beveled rear edge.
 25. The spring clip according to claim 23,wherein the raised portion is surrounded by a bezel.
 26. The spring clipaccording to claim 21, wherein the spring clip is constructed to becompressed by deflecting the first tab by a first angular amount and bydeflecting the second tab by a second angular amount such that a firsttorque exerted on the first tab and a second torque exerted on thesecond tab are substantially equal and opposite.
 27. The spring clipaccording to claim 21, wherein the spring clip and the heat sink form aheat sink assembly, the heat sink assembly is mountable on a cage, andthe cage includes one of an SFP and an XFP cage.
 28. The spring clipaccording to claim 22, wherein the heat sink has a retention slot formedbetween at least some of the fins, the retention slot constructed toreceive at least a portion of a cover fixed to a circuit board.
 29. Aspring clip comprising: a first tab; a second tab; and a serpentineportion interposed between the first tab and the second tab, wherein thespring clip is disposable on a base of a heat sink between finsextending from an upper surface of the base of the heat sink, whereinthe first tab forms a first angle with respect to the upper surface ofthe base of the heat sink, the second tab forms a second angle withrespect to the upper surface of the base of the heat sink, and theserpentine portion extends in its entirety in a plane that issubstantially parallel to the upper surface of the base of the heatsink, the first tab and the second tab are capable of being respectivelycompressed in a direction toward the base of the heat sink, and thespring clip and the heat sink form a heat sink assembly mountable on atleast one cage of a circuit board, each cage having an upper surfaceformed with an opening therethrough.
 30. The spring clip according toclaim 29, wherein the circuit board includes a retaining memberextending across a front edge of the circuit board, the retaining memberretaining the first tab in a compressed state when the heat sinkassembly is mounted on the at least one cage.
 31. The spring clipaccording to claim 29, wherein the circuit board includes an anchorconstructed to retain the second tab in a compressed state when the heatsink assembly is mounted on the at least one cage.
 32. The spring clipaccording to claim 29, wherein a wall of a cover is inserted in aretention slot formed between at least some of the fins of the heat sinkto limit movement of the heat sink with respect to the at least onecage.
 33. The spring clip according to claim 32, wherein the cover hasone or more ventilation openings formed therein.
 34. The spring clipaccording to claim 32, wherein the spring clip is constructed to becompressed by deflecting the first tab by a first angular amount and bydeflecting the second tab by a second angular amount such that a firsttorque exerted on the first tab and a second torque exerted on thesecond tab are substantially equal and opposite.
 35. The spring clipaccording to claim 34, wherein the spring clip is constructed to forcethe heat sink into a seated position in an opening of a respective cagewhen a module is not present in the cage and to force the heat sink intocontact with the module when the module is present in the cage.
 36. Theheat sink attachment system according to claim 35, wherein when the heatsink is in a seated position, at least one portion of the heat sinkextends through the opening of the cage and into the cage.
 37. A heatsink comprising: a base; and fins extending from an upper surface of thebase; wherein a spring clip is disposed on the heat sink between thefins, the spring clip including a first tab, a second tab, and aserpentine portion interposed between the first tab and the second tab,wherein the first tab forms a first angle with respect to the uppersurface of the base of the heat sink, the second tab forms a secondangle with respect to the upper surface of the base of the heat sink,and the serpentine portion extends in its entirety in a plane that issubstantially parallel to the upper surface of the base of the heatsink, the first tab and the second tab are capable of being respectivelycompressed in a direction toward the base of the heat sink, and thespring clip and the heat sink form a heat sink assembly mountable on atleast one cage of a circuit board, each cage having an upper surfaceformed with an opening therethrough.
 38. The heat sink according toclaim 37, further comprising a raised portion extending from a lowerside of the base that is opposite from the upper surface.
 39. The springclip according to claim 38, wherein the raised portion is off-centeralong the lower side of the base.
 40. The spring clip according to claim39, wherein the raised portion has a beveled front edge and a beveledrear edge.